According to a draft report by The National Eye Institute (NEI) at The United States National Institutes of Health (NIH), glaucoma is now the leading cause of irreversible blindness worldwide and the second leading cause of blindness, behind cataract, in the world. Thus, the NEI draft report concludes, “it is critical that significant emphasis and resources continue to be devoted to determining the pathophysiology and management of this disease.” Glaucoma researchers have found a strong correlation between high intraocular pressure and glaucoma.
In addition to drug treatments, a variety of surgical treatments for glaucoma have been described. For example, shunts were implanted to direct aqueous humor from the anterior chamber to the extraocular vein (Lee and Scheppens, “Aqueous-venous shunt and intraocular pressure,” Investigative Ophthalmology (February 1966)). Other early glaucoma treatment implants led from the anterior chamber to a sub-conjunctival bleb (e.g., U.S. Pat. No. 4,968,296 and U.S. Pat. No. 5,180,362). Still others were shunts leading from the anterior chamber to a point just inside Schlemm's canal (Spiegel et al., “Schlemm's canal implant: a new method to lower intraocular pressure in patients with POAG?” Ophthalmic Surgery and Lasers (June 1999); U.S. Pat. No. 6,450,984; U.S. Pat. No. 6,450,984).
More recently, glaucoma treatment devices that are disposed partially or completely within Schlemm's canal have been described. Examples of such devices may be found, e.g., in U.S. Pat. No. 7,740,604; U.S. Patent Publ. No. 2009/0082860; U.S. Patent Publ. No. 2009/0227934; U.S. Patent Publ. No. 2009/0132040; U.S. Patent Publ. No. 2010/0121342; U.S. Patent Publ. No. 2006/0195187; and U.S. application Ser. No. 12/833,863.